Which OSX version suits best for me? Tips?

Hi.
I work in a post production company in Argentina and we are getting a brand new Mac Pro in the next days.

All of our current Mac Pros and iMacs have Snow Leopard 10.6.8 and some have Lion 10.7.2.
The ones with Lion are having some problems (stability, bugs, etc) and we would like to stick with 10.6.8 because it seems to be the best for now.
The problem is that we want to run Resolve and use a GTX570, so we need Lion at least, and as this one will be the most important machine in the place we need it to be as bugfree as possible.

Other softwares that will be in use in the machine are Scratch, SpeedGrade, Final Cut Pro, Adobe Premiere, After Effects...

So I would appreciate tips and recommendation of which version of OSX to use, plus any tools that help with the issues, disabling annoying system settings, etc.